Aqueous dispersions of phenyl-betanaphthylamine



drying of the elastomer.

Patented Apr. 19, 1949 TEN T OFF ICE AQUEOUS DISPERSIONS Fz'PHENY-L-BETA- NAPHTHYLAMINE Bernard M. Stnrgis, Pitman, N. 1.,assignor to E. I. du Pont de Nemours '& Company, 'Wilmington, DeL, acorporation of Delaware No Drawing.

Application January 25, 1946,

Serial N0. 643,483

Claims. 1

This invention relates to the preparation of stable aqueous dispersionsof phenyl-beta-naphthylamine, which are particularly useful asantioxidants in the elastomer field.

The secondary aromatic amines, such as phenyl-beta-naphthylamine, whichare employed as anti-oxidants in the rubber and synthetic rubberindustries, when employed with rubber latices or other aqueousdispersions of synthetic elastomers are preferably incorporated in suchlatices as aqueous dispersions. These aqueous dispersions of the aminesare prepared with the aid of dispersing agents by the methods usuallyemployed for dispersing solids in liquids. Ordinarily, the aromaticamine antioxidant dispersion is made up, as it is used, inconcentrations of from 10% to 60%, and such dispersions are added to thelatex in carefully measured amounts prior to the coagulation and Theaqueous dispersions of the secondary aromatic amines prepared bythemethod-s heretofore employed are often not stable, and, on standing evenfor short periods of time, the amine settles out quite rapidly. Suchsedimentation makes the han- .dling, measuring and proper addition ofthe amine to the latex difficult. When such settling out of thedispersion occurs, it tends to plug pumps, valves and lines. It will bealso be obvious th at in such case the amount of anti-oxidant actuallyadded to the lateX cannot be accurately determined, and therefore it isimportant, for smooth operation of the process, that stable dispersionsof the anti-oxidants be used.

It is difiicult to make stable aqueous dispersions ofphenyl-beta-naphthylamine by the usual methods of dispersing solids inwater, such as by grinding in a ball mill or even with the use of suchefiicient apparatus as the colloid mill. While most of the commercialwetting or .dispersing agents give improved results when added tosuchsuspensions, even the most efiicient dispersing agents often fail toproduce dispersions of phenylebeta-naphthylamine which Will not settleout after short periods of standing. The addition of larger amounts ofthe dispersing agent does not produce the desired stability.

It istherefore an object of this invention to provide a method ofproducing aqueous dispersions of phenyl-beta-naphthylamine with improvedstability with regard to settling. -A-further object of the invention isto produce the phenyl beta-naphthylamine in a form such that it can bereadily dispersed in ---water by the-usual methods, but "which will givesuspensions that are much more stable with regard "to settling than areordinarily obtained. A further object of the invention is to produceaqueous disp sions of phenyl-beta-naphthylamine in higher concentrationsthan .has normallyjbeen possible and which will remain dispersed whendiluted in water for a sufficient time to permit suitable processingoftherubber latices with which they are incorporated.

I have found that greatly improved aqueous dispersions ofphenyl+beta-naphthylamine can he produced vby adding to .:the amine asmall amount of a straight chain aliphatic monocarboigylic acidcontaining from ,9 to 1'4 and preferably L9 to 12 carbon atoms. .Theacidzispreferab'ly added to the amine during the manufactureor flakingprocess, as more particularly illustrated ,in the following examples,although it may be added during the preparation of "the dispersion byadding it *to the aqueous suspension and subjecting the mass toagmilling'or colloidal grinding operation. It appears that the acid mustbe incorporated in such :a'manner'that it has intimate contact with thedispersed ;par- .ticles of the phenyl-betanaphthy1amine, for, by merelyadding the acid to the already-prepared dispersion without againsubjecting the mass to conditions which would ordinarily disperse-thesolid in a liquid, 131'18183111631'65111138 are not obtained as when theacid is added to the amine duringorpriortothe dispersion operation."These acids effective as dispersing aids in "amounts ranging from 0.1%to 19%, although practical limits of use are from 0.1% to 3%, based onthe Weight of the phenyl--beta+naphthylamine. 'Mixtures of acids of thistype'appear'tobeasefiective as the pure acids by themselves.

This invention is "applicable particularly in improving thedispersionstability ofphenyl-betanaphthylam-ine used as an anti-oxidantflfor rubher or. other elastomers.

As pointed out above, theacid may be added to thephenyl-betagnaphthylamine .during, the manufacture of the amine ,oritcanbe intimately incorporated with the amine "by a .mixing or millingoperation so that the amine is put in a form that can be readilydispersed in water by the user by the methods generally employed inpreparing the amine dispersion. Alternatively, the acid can be added tothe water, amine and dispersing agent at the start of the dispersionprocess, or during the dispersion process. These acids will function inany of the common dispersion processes wherein thephenyl-beta-naphthylamine is dispersed in water with a dispersing agent.

The straight chain aliphatic monocarboxylic acids in themselves do notappear to have properties of dispersing agents, and they function as adispersing aid where the phenyl-beta-naphthylamine is dispersed in waterby means of the usual dispersing agents. The preferred dispersing agentis the sodium salts of the reaction product of naphthalene,formaldehyde, and sulfuric acid, as more particularly disclosed in U. S.P. 1,336,759. Other dispersing agents, such as the sodium salts ofsulfated laurol or other alcohols, or mixtures of the same, purifiedsulfolignins, and the sodium salts of aliphatic sulfonates of petroleumhydrocarbons or similar dispersing agents, may be employed in place ofthe sodium salts of the naphtha]ene-formaldehyde-sulfuric acidcondensation product.

The fOllOWiIlg examples are given to illustrate the invention, in whichthe parts used are by weight.

Example 1 One thousand (1000) parts of phenyl-betanaphthylamine andparts of pelargonic acid, CsHmCOOH, were melted and flaked in aconventional drum type fiaker, holding the melted material in the flakerpan at 140 to 150 C. and the surface of the drum at 90 C. The flakedmaterial was then made into an aqueous dispersion by mixing 300 parts ofit, 700 parts of distilled water, and 6 parts of sodium salts of thenaphthalene reaction product above referred to, then grindin thismixture through a Charlotte colloid mill set at 0.0055 inch clearancefor minutes. In order to test its stability, 75 cc. of the resultingdispersion was placed in a 100 cc. graduated cylinder, brought up to 100cc. with distilled water, shaken vigorously, and allowed to stand for 20minutes. No sediment could be seen at the bottom of the cylinder at theend of this time and no sediment remained behind when the liquid wascarefully poured out. On the other hand, when no acid was incorporatedin the amine, the resulting dispersion gave 10.5 cc. of sediment in thetest, and this remained in the cylinder after pouring off the liquid.

Example 2 Capric acid, C9I-119COOH, used in place of polargonic acid inExample 1, gave the same results.

Example 3 Laurie acid, CnI-IzzCOOI-I, used in place of pelargonic acidin Example 1, gave the same results.

Example 4 Myristic acid, C13H27COOH, used in place of pelargonic acid inExample 1, gave a dispersion from which 3 cc. of sediment separated inthe test and .1 .cc. remained as a cake in the cylinder after pouring'out the liquid. This illustrates that, as the number of carbon atoms inthe acid increases, the effectiveness of the acid starts to decreasesomewhat when the number reaches 14, although the C14 acid still isdefinitely effective.

When the number of carbon atoms is less than 9 or more than 14, the acidhas little or no favorable eifect upon the stability of the aminedispersions. The following table further illustrates the relationbetween the chain length of the acid and its effect upon the stability.

Table Sediment No. of C Atoms in the Acid A D or e- Before cantation Cc.Cc.

7. 5 4 8 0 0 0 0 0 0 (l 3 l 0 0 l8 3 It will be seen from this tablethat the most efiective acids are in the narrow range of 9 to 12 carbonatoms. This range, however, is different for the other classes of longchain compounds having this same stabilizing effect. Thus, it is 8 to 18for alcohols, 12 to 16 for the methyl esters of long chain carboxylicacids, in the neighborhood of 15 for long chain ketones, and 8 to 14 forlong chain mercaptans. A further illustration of the highly specificnature of these effects is the observation that the amide, methylolamide, zinc salt, and nitrile of lauric acid are entirely ineffective,although lauric acid itself, as shown in Example 3, is very effective.On the other hand, alpha-bromo-lauric acid is quite similar in itseffect to lauric acid. Another illustration of the effect of smallchanges in structure is the effectiveness of oleic acid in giving stablephenyl-beta-naphthylamine dispersions, compared with the ineffectivenessof stearic acid which differs by only two hydrogen atoms, shown in thelast line of the above table.

The use of the primary straight chain monocarboxylic acids of from 9 to14 carbon atoms enables the production of greatly improved aqueousdispersions of the phenyl-beta-naphthyl-amine. These dispersions beingmore stable, can be used over much longer periods of time withoutsettling out. By the addition of the straight chain acids of the typedescribed as a dispersing aid, greatly improved dispersions areobtained, usually being much smaller in particle size, having lowerviscosity for a given concentration, and havin less tendency to foam. Bythe addition of these dispersing aids much smaller amounts of thedispersing agent may be employed.

The dispersions formed according to the present invention may be addedto any aqueous dispersion of oxidizable organic materials requiringstabilization by means of secondary aromatic amines.

I claim:

1. In the process for preparing aqueous dispersions ofphenyl-beta-naphthylamine wherein the phenyl-beta-naphtylamine isdispersed in water by means of a water soluble dispersing agent, thesteps which comprise incorporating in such aqueous dispersion, beforethe dispersion process is completed, from 0.1% to 10%, based on theweight of the amine, of a straight chain aliphatic monocarboxylic acidcontaining from 9 to 14 carbon atoms, and completing the dispersionprocess by a colloidal mixing operation.

2. The process for preparing aqueous dispersions ofphenyl-beta-naphthylamine, which comprises intimately incorporating inthe phenyl beta-naphthylamine from 0.1% to 10%, based on the weight ofthe amine, of a primary straight chain aliphatic monocarboxylic acidcontaining from 9 to 14 carbon atoms, and dispersing the resultingproduct in water with the aid of a water soluble dispersing agent and acolloidal mixing operation.

3. An aqueous dispersion of phenyl-betanaphthylamine which has beenprepared. by a colloidal mixing operation and which in addition to thewater and phenyl-beta-naphthylamine consists of a water solubledispersing agent and as a dispersion aid from 0.1% to 10%, based on theweight of the amine, of a straight chain aliphatic monocarboxylic acidcontaining from 9 to 14 carbon atoms, which dispersing aid wasincorporated in the dispersion prior to completion of the colloidalmixing operation.

4. An aqueous dispersion of phenyl-beta-naphthylamine which has beenprepared by a colloidal mixing operation and which in addition to thewater and phenyl-beta-naphthylamine consists of a water solubledispersing agent and as a dispersion aid from 0.1% to 10%, based on theweight of the amine, of pelargonic acid, which dispersing aid wasincorporated in the dispersion prior to completion of the colloidalmixing operation.

5. An aqueous dispersion of phenyl-betanaphthylamine which has beenprepared by a colloidal mixing operation and which in addition to thewater and phenyl-beta-naphthylamine consists of a water solubledispersin agent and as a dispersion aid from 0.1% to 10%, based on theweight of the amine, of capric acid, which dispersing aid wasincorporated in the dispersion prior to completion of the colloidalmixing operation.

6. An aqueous dispersion of phenyl-betanaphthylamine which has beenprepared by a colloidal mixing operation and which in addition to theWater and phenyl-beta-naphthylamine consists of a water solubledispersing agent and as a dispersion aid from 0.1% to 10%, based priorto completion of the colloidal mixing opertion.

7. A phenyl-beta-naphthylamine composition which is readily dispersiblein water by a colloidal mixing operation with the aid of a water solubledispersing agent to give a dispersion which has improved stability withregard to settling, consisting of phenyl-beta-naphthylamine havingintimately incorporated therewith from 0.1% to 10%, based on the weightof the amine, of a straight chain aliphatic monocarboxylic acidcontaining from 9 to 14 carbon atoms.

8. A phenyl-beta-naphthylamine composition which is readily dispersiblein water by a colloidal mixin operation with the aid of a water solubledispersing agent to give a dispersion which has improved stability withregard to settling, consisting of phenyl-beta-naphthylamine havingintimately incorporated therewith from 0.1% to 10%, based on the weightof the amine, of pelargonic acid.

9. A phenyl-beta-naphthylamine composition which is readily dispersiblein water by a colloidal mixing operation with the aid of a water solubledispersing agent to give a dispersion which has improved stability withregard to settling, consisting of phenyl-beta-naphthylamine havingintimately incorporated therewith from 0.1% to 10%, based on the weightof the amine, of capric acid.

10. A phenyl-beta-naphthylamine composition which is readily dispersiblein water by a colloidal mixing operation with the aid of a water solubledispersing agent to give a dispersion which has improved stability withregard to settling, consisting of phenyl-beta-naphthylamine havingintimately incorporated therewith from 0.1% to 10%, based on the weightof the amine, of lauric acid.

BERNARD M. STURGIS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,467,197 Russell Sept. 4, 19231,977,211 Schur Oct. 16, 1934 2,100,714 Hiers Nov. 30, 1937 2,327,975Zaucker Aug. 24, 1943

